Merge pull request earthobservations#62 from panodata/periodtype-sort…

…able

Make PeriodType enumeration sortable

python_dwd/enumerations/period_type_enumeration.py

@@ -1,10 +1,55 @@
 """ enumeration for period_type """
 from enum import Enum
+import functools
 
 
+"""
+Following this: https://stackoverflow.com/questions/39268052/how-to-compare-enums-in-python
+Ordering is required for the PeriodType enumeration in order for it to be sorted.
+PeriodType needs to be sortable for the request definition where for the case of
+requesting data for several periods, we want preferably the historical data with
+quality marks and drop overlapping values from other periods.
+"""
+
+
+@functools.total_ordering
 class PeriodType(Enum):
     """ enumeration for different period types of storages on dwd server"""
+    """ enumeration for different period types of storage on dwd server"""
+    @property
+    def _period_type_order_mapping(self):
+        # IMPORTANT: THIS DEPENDS ON THE NAMING CONVENTIONS USED IN THE PeriodType
+        # ENUMERATION AS SHOWN BELOW
+        return {
+            "HISTORICAL": 0,
+            "RECENT": 1,
+            "NOW": 2,
+            "ROW": 3
+        }
+
     HISTORICAL = "historical"
     RECENT = "recent"
     NOW = "now"
     ROW = ""
+
+    def __lt__(self, other):
+        if self.__class__ is other.__class__:
+            return self._period_type_order_mapping[self.name] < \
+                   self._period_type_order_mapping[other.name]
+        return NotImplemented
+
+    def __gt__(self, other):
+        if self.__class__ is other.__class__:
+            return self._period_type_order_mapping[self.name] > \
+                   self._period_type_order_mapping[other.name]
+        return NotImplemented
+
+    def __ge__(self, other):
+        if self.__class__ is other.__class__:
+            return not self.__lt__(other)
+        return NotImplemented
+
+    def __le__(self, other):
+        if self.__class__ is other.__class__:
+            return not self.__gt__(other)
+        return NotImplemented